1. Field of the Invention
The present invention relates to a plating method and a plating apparatus which can be advantageously used for supplying a plating solution to a surface to be plated of a substrate, such as a semiconductor substrate, and forming, e.g., a circuit pattern of interconnects in the surface to be plated of the substrate.
2. Description of the Related Art
A plating apparatus has been known which processes a surface to be plated of a substrate with the surface to be plated facing downwardly (face down) (see, for example, Japanese Patent Laid-Open Publication No. 2005-2455). This plating apparatus uses a resistor body (impregnation member) provided between a substrate and an anode in order to carry out uniform plating of the surface to be plated of the substrate.
When carrying out plating of a substrate in a face-down manner, the substrate is lowered from above a plating solution held in a plating cell so as to bring the surface to be plated of the substrate into contact with the plating solution. When the substrate is lowered while keeping the surface to be plated parallel to a surface of the plating solution, air bubbles may intrude into the interface between the substrate and the plating solution. This causes the problem that there will be non-contact portions of the surface to be plated with the plating solution due to the presence of the air bubbles, resulting in non-uniform plating of the surface to be plated of the substrate. The provision of a resistor body between a substrate and an anode involves the problem that the resistor body produces heat when applying current on plating, causing a rise of the temperature of the plating solution.
An air-bubble removal method has therefore been practiced which involves creating an upward flow of plating solution, flowing from a lower position in a plating cell toward the liquid surface, in the plating solution in the plating cell to raise the center of the liquid surface, thereby forcing air bubbles, which accumulate on the lower surface of a substrate upon its contact with the plating solution, out of the substrate. However, in the case where a resistor body is disposed between an anode and a substrate as described above, the upward flow of plating solution toward the liquid surface is blocked by the resistor body, whereby a raised portion cannot be formed in the liquid surface. Thus, in the case of a face-down type of plating apparatus which uses a resistor body, it has been difficult to remove air bubbles which accumulate on the lower surface of a substrate upon its contact with a plating solution. In order to enhance the in-plane uniformity of a thickness of a plated film by the use of a resistor body, it is necessary to shut off current pathways other than those current pathways which run through the resistor body and to dispose the resistor body at a small distance, such as not more than 5 mm, from a substrate. It has been difficult, however, to allow a plating solution, whose temperature is regulated in consideration of the heat produced by the resistor body, to flow smoothly in such a narrow space between the substrate and the resistor body without stagnation.